A method to search using tags and boolean operators (and / or / not) was presented here, though it does not appear to be a feature through the standard UI.
It looks like the feature was considered in the steemapi [source], but has since been abandonded [source].
It should be a part of standard UI so that everybody knows and can use it. Any specific reason why it was abandoned?
Here's the closing comment from github:
I like the idea of adding specific queries to my feed, but for the time being the search feature will have to suffice:
